This invention relates to torque converter and clutch assemblies, and more particularly, to such assemblies wherein a friction interface is disposed on the turbine. Specifically, this invention relates to such assemblies having an inertial mass secured to the turbine on which a friction interface is provided for improved clutch engagement.
Prior art torque converter and clutch assemblies incorporate a pressure plate with a friction disc bonded thereto and disposed for axial displacement for engagement with the input shell of the torque converter. The input shell of the torque converter generally has a machined surface thereon which provides the frictional interface for the friction disc and pressure plate. Due to tolerances and manufacturing methods, the alignment of the annular surface of the friction disc and the input shell is not ideal. In other words, there are imperfections such as waviness or conical configurations which prevent the frictional surfaces from providing a continuous annular engagement.
Prior art torque converter and clutch assemblies have attempted solutions to this problem including the use of an elastomer disc bonded between the friction material and the pressure plate. This solution does afford some degree of relief for the problem, however, the bonding material and the elastomer disc must be sufficiently strong to withstand the stresses present during the transmission of torque between the input shell and the pressure plate. This torque transmission results in shear forces being imposed on the elastomer disc and between the elastomer disc and its bonded surfaces. Since these shear forces can be quite large and have a detrimental affect on the elastomer material, the useful life of the clutch is shortened and/or the cost of bonding, bonding materials and elastomer materials is greatly increased.
Another prior art arrangement, described in U.S. Ser. No. 07/881,107, filed May 11, 1992, Hageman et al., assigned to the assignee of this invention, provides a compliant interface between the pressure plate, friction surface and the input shell. In this arrangement, a friction disc is disposed on a separate rigid member which is substantially rotatably secure with the pressure plate while being axially movable relative thereto. An elastomeric covered metal disc is disposed between the friction disc and the pressure plate and is made rotatably fast with the friction disc.
The friction performance of a torque converter clutch (TCC), during the apply and release transients and during engaged operation, is dependent on the performance of the friction system determined by the operating conditions, geometry and frictional characteristics of interacting mechanical components and the friction modifying characteristics of the surrounding oil. A well controlled friction system is expected to yield predictable operating characteristics and assist in system tuning for optimal performance and pleaseability of the TCC system. Friction system characteristics, which affect performance, include friction material operating characteristics and geometry and reaction surface operating characteristics, geometry and surface texture.
The dynamic response of a vibrating system affects perceived performance and is primarily characterized by the natural frequency of the system, as well as the amplitude and phase relationship of the vibrating members of the system. System tuning of these characteristics is generally undertaken in such a manner as to avoid undesirable disturbances within the operating range of the system.
There are several possible methods for tuning the dynamic response of automatic transmission driveline systems. Classically, isolator springs or damper springs are tuned to adjust the dynamic response of the driveline for the purpose of isolating or avoiding disturbances during TCC engaged operation and thus provide a pleaseable driveline "feel" in the vehicle. Several other means exist to tune the system. System rotational inertias, damping, hysteresis and system forcing function (gas torque from the engine) can be designed, tweaked or tuned to provide various steady state response characteristics. System hysteresis and damping can be used to tune the system for various transient response characteristics, such as shudder. One such system is described in U.S. Ser. No. 07/877,509, filed May 1, 1992, Poorman et al., and assigned to the assignee of the present invention. Another system with improved inertia tuning is described in U.S. Pat. No. 5,121,821, issued Jun. 16, 1992, to Poorman et al., and assigned to the assignee of the present invention.